Synthesis and structures of bimetallic silicon-containing imido alkylidene complexes of tungsten (R′O)2(ArN)WCH-SiR2-CHW(NAr)(OR′)2 (R = Me, Ph) and (R′O)2(ArN)WCH-SiMe2SiMe2-CHW(NAr)(OR′)2

Bimetallic alkylidene complexes of tungsten (R′O)₂(ArN)WCH-SiR₂-CHW(NAr)(OR′)₂ (R = Me (1), Ph (2)) and (R′O)₂(ArN)WCH-SiMe₂SiMe₂-CHW(NAr)(OR′)₂ (3) (Ar = ; R′ = CMe₂CF₃) have been prepared by the reactions of divinyl silicon reagents R₂Si(CHCH₂)₂ with known alkylidene compounds R′′-CHMo(NAr)(OR′)₂. (R′′ = Bu^t, PhMe₂C) Complexes 1-3 were structurally characterized. Ring opening metathesis polymerization (ROMP) of cyclooctene using compounds 1-3 as initiators led to the formation of high molecular weight polyoctenamers with predominant trans-units content in the case of 1 and 3 and predominant cis-units content in the case of 2.     

The synthesis and single-crystal X-ray structures of palladium(II) and platinum(II) complexes of the difluorovinyl and 1-chloro-2-fluorovinyl-substituted phosphines, PPh2(Z-CFCFH) and PPh2(E-CClCFH)

The coordination chemistry of the fluorovinyl substituted phosphines PPh₂(Z-CFCFH) and PPh₂(E-CClCFH) with K₂MX₄ (M = Pd, Pt; X = Cl, Br, and I) salts has been investigated resulting in the first reported palladium(II) and platinum(II) complexes of phosphines containing partially fluorinated vinyl groups. The complexes have been characterised by a combination of multinuclear [¹H, ¹³C{¹H}, ¹⁹F, ³¹P{¹H}] NMR spectroscopy, and IR/Raman spectroscopy. The single-crystal X-ray structures of trans-[PdX₂{PPh₂(CFCFH)}₂], X = Cl (1), Br (2), I (3), trans-[PdCl₂{PPh₂(CClCFH)}₂] (4), cis-[PtX₂{PPh₂(CFCFH)}₂], X = Cl (5), Br (6), trans-[PtI₂{PPh₂(CFCFH)}₂] (7), and both cis- and trans-[PtCl₂{PPh₂(CClCFH)}₂] (8), have been determined. Results obtained from spectroscopic and crystallographic data suggest that replacement of a β-fluorine by hydrogen, whilst reducing the steric demand of the ligand, has little effect on the electronic character of the ligand. The presence of a proton in the vinyl group results in short proton-halide secondary interactions in the solid state (d(H?X) = 2.72(3) for 1, and 2.92(5) Å for 2) forming an infinite chain ribbon motif.     

Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η-diphosphine ligand

Treatment of the thiosemicarbazones 2-XC₆H₄C(Me)NN(H)C(S)NHR (R = Me, X = F, a; R = Et, X = F, b; R = Me, X = Cl, c; R = Et, X = Br, d) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid, as appropriate, gave the tetranuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}]₄ (1a-1d). Reaction of 1a-1d with the diphosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp) or trans-Ph₂PCHCHPPh₂ (trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC₆H₃C(Me)NNC(S)-NHR]}₂(μ-diphosphine-P,P)] (2a-5a, 3b, 3d, 4c, 5c). Reaction of 1a, 1b with the short-bite or long-bite diphosphines, dppm or cis-dpe, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}(diphosphine-P)] (6a, 6b, 7a). The molecular structure of ligand a and of complexes 1a, 3d, 5a, 5c, 6a, 6b and 7a have been determined by X-ray diffraction analysis. The structure of complex 7a shows that the long-bite cis-bis(diphenylphosphino)ethene phosphine appears as monodentate with an uncoordinated phosphorus donor atom.     

Synthesis and characterization of (CHCH)n-bridged (n = 1, 2, 3) heterobimetallic and trimetallic ferrocene-ruthenium complexes

A series of heterobinuclear ferrocene-ruthenium complexes Fc(CHCH)_nRuCl(CO)(PMe₃)₃ (n = 1, 3; n = 2, 12), Fc(CHCH)RuCl(CO)(Py)(PPh₃)₂ (4), and trimetallic Fc(CHCH)RuCl(CO)(PPh₃)₂(Py-E-(CHCH)Fc) (6) have been prepared. The length of the molecular rods is extended by successive insertion of CHCH spacers in the bridging ligands or the ancillary ligands. The respective products have been fully characterized and the structures of 3 and 12 have been established by X-ray crystallography. Electrochemical studies have revealed that ethenyl heterobimetallic complexes display two successive one-electron processes, and that intermetallic electronic communication between the two endgroups is attenuated with the increase of the length of the conjugated bridge. The electrochemical behavior of the trimetallic complex reveals strong electronic communication between ruthenium and ferrocene transmitted through the ethenyl bridge, however, it also reveals a very weak interaction between ruthenium and ferrocene transmitted through the (E)-CHCH-Py bridge.     

Synthesis, characterization and solid state structures of thiosemicarbazone palladacycles: Influence of hydrogen bonding in the molecular arrangement

Treatment of the thiosemicarbazones 4-FC₆H₄C(Me)NN(H)C(S)NHR, (R = Me, a; Ph, b) and 2-ClC₆H₄C(Me)NN(H)C(S)NHR (R = Ph, c) with lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid gave the tetranuclear cyclometallated complex [Pd{4-FC₆H₃C(Me)NNC(S)NHR}]₄ (1a, 1b) and [Pd{2-ClC₆H₃C(Me)NNC(S)NHPh}]₄ (1c). Reaction of these tetramers with the diphosphines dppe, t-dppe, dppp or dppb in a 1:2 molar ratio gave the dinuclear cyclometallated complexes [(Pd{4-FC₆H₃C(Me)NNC(S)NHR})₂(μ-Ph₂P(CH₂)_nPPh₂)], (n = 2, 2a, 2b; 3, 4a, 4b; 4, 5a, 5b), [(Pd{4-FC₆H₃C(Me)NNC(S)NHPh})₂(μ-Ph₂PCHCHPPh₂)], (3a, 3b) and [(Pd{2-ClC₆H₃C(Me)NNC(S)NHR})₂(μ-Ph₂P(CH₂)_nPPh₂)], (n = 2, 2c, 2d; 3, 4c, 4d; 4, 5c, 5d), [(Pd{2-ClC₆H₃C(Me)NNC(S)NHPh})₂(μ-PPh₂CHCHPPh₂)], (3c, 3d). The X-ray crystal structure of the ligand b and the complexes 3c, 4a and 4d were determined. The structures of complexes 4a and 4d show that the different disposition of the chain cyclometallated of the thiosemicarbazones (in the same orientation or in the opposite one) is due to the different H bonds produced.     

Reactions of cyano(alkynyl)ethenes with some alkynyl- and diynyl-ruthenium complexes

Reactions of Ru(CCPh)(PPh₃)₂Cp with (NC)₂CCR¹R² (R¹ = H, R² = CCSiPrⁱ₃8; R¹ = R² = CCPh 9) have given η³-butadienyl complexes Ru{η³-C[C(CN)₂]CPhCR¹R²}(PPh₃)Cp (11, 12), respectively, by formal [2 + 2]-cycloaddition of the alkynyl and alkene, followed by ring-opening of the resulting cyclobutenyl (not detected) and displacement of a PPh₃ ligand. Deprotection (tbaf) of 11 and subsequent reactions with RuCl(dppe)Cp and AuCl(PPh₃) afforded binuclear derivatives Ru{η³-C[C(CN)₂]CPhCHCC[ML_n]}(PPh₃)Cp [ML_n = Ru(dppe)Cp 19, Au(PPh₃) 20]. Reactions between 8 and Ru(CCCCR)(PP)Cp [PP = (PPh₃)₂, R = Ph, SiMe₃, SiPrⁱ₃; PP = dppe, R = Ph] gave η¹-dienynyl complexes Ru{CCC[C(CN)₂]CRCH[CC(SiPrⁱ₃)]}(PP)Cp (15-18), respectively, in reactions not involving phosphine ligand displacement. The phthalodinitrile C₆H(CCSiMe₃)(CN)₂(NH₂)(SiMe₃) 10 was obtained serendipitously from (Me₃SiCC)₂CO and CH₂(CN)₂, as shown by an XRD structure determination. The XRD structures of precursor 7 and adducts 11, 12 and 17 are also reported.     

Crystal structures of amarine and isoamarine and copper(I) coordination chemistry with their allylation products

The crystal structures of amarine (1) and isoamarine (2), important intermediates in the preparation of 1,2-diphenyl-diaminoethane, were successfully determined. Their allylation products, 1,3-diallyl amarine (1)(CH₂CHCH₂)₂Br (3) and isoamarine bromide (2)(CH₂CHCH₂)₂Br (4) [the crystal structures of (1)(CH₂CHCH₂)₂PF₆(3-Br + PF₆) and (2)(CH₂CHCH₂)₂PF₆ (4-Br + PF₆) are also successfully determined to confirm allylation products], react with CuBr to afford (1)₂(CH₂CHCH₂)₄(Cu₂Br₄) (5) and (2)(CH₂CHCH₂)₂(Cu₂Br₃) (6), respectively. Crystal structures of 5 and 6 reveal that 5 is an anion discrete complex without olefin moiety coordination, and 6 has a 1D infinite chain with olefin moiety coordination as a bridging spacer. The fluorescent emission spectra of 5 (λ_emax = 570 nm) and 6 (λ_emax = 642 nm) were measured, and display a significant difference that can be used for solid state fluorescent sensing them.     

Linear homobimetallic palladium complexes with end-capped SC(O)Me units

Rigid-rod structured homobimetallic palladium complexes of type [{trans-(Me(O)CS-4-C₆H₄-C₆H₄)(Ph₃P)₂Pd}₂(μ-N^∩N)](OTf)₂ (8a, μ-N^∩N = 4,4′-bipyridine, bpy; 8b, μ-N^∩N = C₅H₄N-CHN-NCH-C₅H₄N; 8c, μ-N^∩N = C₅H₄N-CHCH-C₆H₄-CHCH-C₅H₄N; 8d, μ-N^∩N = C₅H₄N-CHN-C₆H₄-NCH-C₅H₄N) were synthesized by the reaction of trans-[(Me(O)CS-4-C₆H₄-C₆H₄)(Ph₃P)₂Pd](OTf) (6) with 0.5 equivalents of N^∩N (7a, N^∩N = bpy; 7b, N^∩N = C₅H₄N-CHN-NCH-C₅H₄N; 7c, N^∩N = C₅H₄N-CHCH-C₆H₄-CHCH-C₅H₄N; 7d, N^∩N = C₅H₄N-CHN-C₆H₄-NCH-C₅H₄N) in high yield. Complex 6 was accessible by the subsequent reaction of I-4-C₆H₄-C₆H₄-4′-SC(O)Me (2) with [(PPh₃)₄Pd] (3) to produce trans-[(I)(Me(O)CS-4-C₆H₄-C₆H₄)(Ph₃P)₂Pd] (4) which further reacted with AgOTf (5) to give 6.The structures of 4 and 8c in the solid state are reported. Most characteristic for these systems is the square-planer coordination geometry of palladium with trans-positioned PPh₃ groups. This automatically positions the iodo ligand and the Me(O)CS-4-C₆H₄-C₆H₄ unit (complex 4) or the nitrogen donor atoms of the C₅H₄N-CHCH-C₆H₄-CHCH-C₅H₄N connectivity and the thio-acetyl group Me(O)CS-C₆H₄-C₆H₄ (complex 8c) trans to each other. In 8c a Pd-Pd separation of 20.156 Å is typical.The electrochemical redox behavior of 2, 4 and 8 is discussed.     

Effect of ketimide ligand for ethylene polymerization and ethylene/norbornene copolymerization catalyzed by (cyclopentadienyl)(ketimide)titanium complexes-MAO catalyst systems: Structural analysis for CpTiCl2(NCPh2)

Ligand effects on the catalytic activity [and norbornene (NBE) incorporation] for both ethylene polymerization and ethylene/NBE copolymerization using half-titanocenes (titanium half-sandwich complexes) containing ketimide ligand of type Cp′TiCl₂[NC(R¹)R²] [Cp′ = Cp (1), C⁵Me⁵ (Cp^∗, 2); R¹,R² = ^tBu,^tBu (a), ^tBu,Ph (b), Ph,Ph (c)]-methylaluminoxane (MAO) catalyst systems have been investigated. CpTiCl₂[NC(^tBu)Ph] (1b) CpTiCl₂(NCPh₂) (1c), and Cp^∗TiCl₂(NCPh₂) (2c) were prepared and identified; the structure of Cp^∗TiCl₂(NCPh₂) (2c) was determined by X-ray crystallography. The catalytic activity for ethylene polymerization increased in the order: 1a > 1b > 1c, suggesting that an electronic nature of the ketimide ligand affects the activity. However, molecular weight distributions for resultant (co)polymers prepared by 1b,c and by 2c-MAO catalyst systems were bi- or multi-modal, suggesting that the ketimide substituent plays a key role in order for these (co)polymerizations to proceed with single catalytically-active species. CpTiCl₂(NC^tBu₂) (1a) exhibited both remarkable catalytic activity and efficient NBE incorporation for ethylene/NBE copolymerization.